Radiation-resistant properties of cross-linking PTFE for medical use

The property changes of two types of partially cross-linking PTFE (XF1B) and totally cross-linking PTFE (XF2) treated by Co-60 γ-rays were examined physically and chemically. The PTFEs were subjected to a tensile strength test, observation by digital microscope, X-ray diffraction, and Raman analysis. XF1B clearly showed a decrease in the tensile breaking strength at 1 kGy, while XF2 showed a decrease in the tensile breaking strength at a higher irradiation dose, 50 kGy. X-ray diffraction revealed an increase in the (004) peak intensity of XF1B after irradiation. On the other hand, the increase was not proportional to the irradiation dosages. An increase in the peak intensity was not observed in XF2. These results suggest that crystallization by irradiation advanced in XF1B, and the structural change was not significant in XF2. Raman analysis showed an increase in the spectral intensity of XF1B with increasing irradiation dosages, and no significant change in the spectral intensity of XF2. It was suggested that XF1B had been broken down into constituent subunits. The cross-linking PTFEs used in this study did not show marked differences in mechanical or chemical properties when compared with those of non-cross-linking PTFE previously reported. Particularly, it is considered that the mechanical deterioration of XF2 by irradiation was inhibited. Therefore, totally cross-linking PTFE is expected to be a useful medical material for sterilization by irradiation.